1
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Dennis FM, Romero Arenas A, Rodgers G, Shanmugam M, Andrews JA, Peralta-Arriaga SL, Partridge BM. Cu-Catalyzed Coupling of Aliphatic Amines with Alkylboronic Esters. Chemistry 2024; 30:e202303636. [PMID: 38168746 DOI: 10.1002/chem.202303636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 12/28/2023] [Accepted: 01/02/2024] [Indexed: 01/05/2024]
Abstract
We report a Cu-catalyzed oxidative coupling of aliphatic amines with benzylic and aliphatic boronic esters to give high value alkyl amines, products found widely in applications from medicinal chemistry to materials science. This operationally simple reaction, which can be performed on gram scale, runs under mild conditions and exhibits broad functional group tolerance. The terminal oxidant of the reaction is O2 from the air, avoiding the need for additional chemical oxidants. Investigation into the reaction mechanism suggests that the boronic ester is activated by an aminyl radical, formed through oxidation of the amine by the Cu catalyst, to give a key alkyl radical intermediate. To demonstrate its utility and potential for late-stage functionalization, we showcase the method as the final step in the total synthesis of a TRPV1 antagonist.
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Affiliation(s)
- Francesca M Dennis
- Department of Chemistry, University of Sheffield, Dainton Building, Sheffield, S3 7HF, United Kingdom
| | - Antonio Romero Arenas
- Department of Chemistry, University of Sheffield, Dainton Building, Sheffield, S3 7HF, United Kingdom
| | - George Rodgers
- Department of Chemistry, University of Sheffield, Dainton Building, Sheffield, S3 7HF, United Kingdom
| | - Muralidharan Shanmugam
- Department of Chemistry and Photon Science Institute, The University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Jonathan A Andrews
- Department of Chemistry, University of Sheffield, Dainton Building, Sheffield, S3 7HF, United Kingdom
| | | | - Benjamin M Partridge
- Department of Chemistry, University of Sheffield, Dainton Building, Sheffield, S3 7HF, United Kingdom
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2
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Nolte TM. 300-fold higher neuro- and immunotoxicity from low-redox transformation of carbamazepine. Toxicol Rep 2023; 11:319-329. [PMID: 37927955 PMCID: PMC10622881 DOI: 10.1016/j.toxrep.2023.09.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 09/19/2023] [Accepted: 09/20/2023] [Indexed: 11/07/2023] Open
Abstract
Current challenges in (eco)toxicology are in understanding the transformation of (reactive) substances, and how transformation affects toxic modes of action. Empirical assessment of transformation products of, practically an infinite number of substances, via experimentation, is impossible. Predicting transformation products for (benchmarking) compounds from conditions, facilitates risk analyses. This study applied calculus to predict transformation products of an important environmental and medicinal/toxicological marker, carbamazepine. As radicals are ubiquitous in humans and the environment, we looked into radical-mediated transformations of carbamazepine as a benchmark. We calculated proportions of their speciation states as function of redox conditions, which we took as pH and O2 concentration, describing transformation via covalent and ionic interactions. Formation of ring-contracted products with neuro-immunological activity is thermodynamically favored under anaerobic conditions and at low pH. Experimentally observed product distributions and toxicities reflect that pattern. Our predictive method may support toxicity predictions for other substances and conditions 'similar' to the current case study via interpolation. This paves the way for a more coherent, effective and easier risk assessment of transformation products.
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Affiliation(s)
- Tom M. Nolte
- Department of Environmental Science, Institute for Water and Wetland Research, Radboud, University Nijmegen, 6500 GL Nijmegen, the Netherlands
- Eidgenössische Technische Hochschule (ETH) Zurich, Laboratory of Inorganic Chemistry, Vladimir-Prelog-Weg 1, 8093 Zurich, Switzerland
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3
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Li QY, Cheng S, Ye Z, Huang T, Yang F, Lin YM, Gong L. Visible light-triggered selective C(sp 2)-H/C(sp 3)-H coupling of benzenes with aliphatic hydrocarbons. Nat Commun 2023; 14:6366. [PMID: 37821440 PMCID: PMC10567795 DOI: 10.1038/s41467-023-42191-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 10/02/2023] [Indexed: 10/13/2023] Open
Abstract
The direct and selective coupling of benzenes with aliphatic hydrocarbons is a promising strategy for C(sp2)-C(sp3) bond formation using readily available starting materials, yet it remains a significant challenge. In this study, we have developed a simplified photochemical system that incorporates catalytic amounts of iron(III) halides as multifunctional reagents and air as a green oxidant to address this synthetic problem. Under mild conditions, the reaction between a strong C(sp2)-H bond and a robust C(sp3)-H bond has been achieved, affording a broad range of cross-coupling products with high yields and commendable chemo-, site-selectivity. The iron halide acts as a multifunctional reagent that responds to visible light, initiates C-centered radicals, induces single-electron oxidation to carbocations, and participates in a subsequent Friedel-Crafts-type process. The gradual release of radical species and carbocation intermediates appears to be critical for achieving desirable reactivity and selectivity. This eco-friendly, cost-efficient approach offers access to various building blocks from abundant hydrocarbon feedstocks, and demonstrates the potential of iron halides in sustainable synthesis.
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Affiliation(s)
- Qian-Yu Li
- Key Laboratory of Chemical Biology of Fujian Province, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, 361005, China
| | - Shiyan Cheng
- Key Laboratory of Chemical Biology of Fujian Province, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, 361005, China
| | - Ziqi Ye
- Key Laboratory of Chemical Biology of Fujian Province, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, 361005, China
| | - Tao Huang
- Key Laboratory of Chemical Biology of Fujian Province, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, 361005, China
| | - Fuxing Yang
- Key Laboratory of Chemical Biology of Fujian Province, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, 361005, China
| | - Yu-Mei Lin
- Key Laboratory of Chemical Biology of Fujian Province, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, 361005, China.
| | - Lei Gong
- Key Laboratory of Chemical Biology of Fujian Province, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, 361005, China.
- Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen, 361005, China.
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4
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Cook A, MacLean H, St. Onge P, Newman SG. Nickel-Catalyzed Reductive Deoxygenation of Diverse C–O Bond-Bearing Functional Groups. ACS Catal 2021. [DOI: 10.1021/acscatal.1c03980] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Adam Cook
- Centre for Catalysis Research and Innovation, Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada
| | - Haydn MacLean
- Centre for Catalysis Research and Innovation, Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada
| | - Piers St. Onge
- Centre for Catalysis Research and Innovation, Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada
| | - Stephen G. Newman
- Centre for Catalysis Research and Innovation, Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada
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5
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Sahharova LT, Gordeev EG, Eremin DB, Ananikov VP. Pd-Catalyzed Synthesis of Densely Functionalized Cyclopropyl Vinyl Sulfides Reveals the Origin of High Selectivity in a Fundamental Alkyne Insertion Step. ACS Catal 2020. [DOI: 10.1021/acscatal.0c02053] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Liliya T. Sahharova
- Zelinsky institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow 119991, Russia
| | - Evgeniy G. Gordeev
- Zelinsky institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow 119991, Russia
| | - Dmitry B. Eremin
- Zelinsky institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow 119991, Russia
- The Bridge@USC, University of Southern California, 1002 Childs Way, Los Angeles, California 90089-3502, United States
| | - Valentine P. Ananikov
- Zelinsky institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow 119991, Russia
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6
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Kato Y, Otomura N, Hirano K, Miura M. Synthesis of DPPP- and DPPPEN-Type Bidentate Ligands by Ring-Opening Diphosphination of Methylene- and Vinylcyclopropanes under Visible-Light-Promoted Photoredox Catalysis. J Org Chem 2020; 85:5981-5994. [PMID: 32252529 DOI: 10.1021/acs.joc.0c00417] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A ring-opening diphosphination of methylene- and vinylcyclopropanes with tetraaryldiphosphines (Ar2P-PAr2) has been developed to afford the corresponding 1,3-diphenylphosphinopropane- and 1,3-diphenylphosphinopentane-type bidentate ligands, respectively. The reaction proceeds under bromine cation-initiated, visible-light-promoted photoredox catalysis at ambient temperature. Owing to the ready availability of functionalized diphosphines, the electronically diverse MeO- and CF3-substituted bidentate ligands are also easily prepared.
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Affiliation(s)
- Yugo Kato
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Nobutaka Otomura
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Koji Hirano
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Masahiro Miura
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
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7
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Biegasiewicz KF, Cooper SJ, Gao X, Oblinsky DG, Kim JH, Garfinkle SE, Joyce LA, Sandoval BA, Scholes GD, Hyster TK. Photoexcitation of flavoenzymes enables a stereoselective radical cyclization. Science 2020; 364:1166-1169. [PMID: 31221855 DOI: 10.1126/science.aaw1143] [Citation(s) in RCA: 200] [Impact Index Per Article: 50.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 05/29/2019] [Indexed: 12/21/2022]
Abstract
Photoexcitation is a common strategy for initiating radical reactions in chemical synthesis. We found that photoexcitation of flavin-dependent "ene"-reductases changes their catalytic function, enabling these enzymes to promote an asymmetric radical cyclization. This reactivity enables the construction of five-, six-, seven-, and eight-membered lactams with stereochemical preference conferred by the enzyme active site. After formation of a prochiral radical, the enzyme guides the delivery of a hydrogen atom from flavin-a challenging feat for small-molecule chemical reagents. The initial electron transfer occurs through direct excitation of an electron donor-acceptor complex that forms between the substrate and the reduced flavin cofactor within the enzyme active site. Photoexcitation of promiscuous flavoenzymes has thus furnished a previously unknown biocatalytic reaction.
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Affiliation(s)
| | - Simon J Cooper
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Xin Gao
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Daniel G Oblinsky
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Ji Hye Kim
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | | | - Leo A Joyce
- Department of Process Research and Development, Merck, Rahway, NJ 07065, USA
| | | | - Gregory D Scholes
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Todd K Hyster
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA.
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8
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Smith AJ, Dimitrova D, Arokianathar JN, Kolodziejczak K, Young A, Allison M, Poole DL, Leach SG, Parkinson JA, Tuttle T, Murphy JA. New reductive rearrangement of N-arylindoles triggered by the Grubbs-Stoltz reagent Et 3SiH/KO t Bu. Chem Sci 2020; 11:3719-3726. [PMID: 34094060 PMCID: PMC8152433 DOI: 10.1039/d0sc00361a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
N-Arylindoles are transformed into dihydroacridines in a new type of rearrangement, through heating with triethylsilane and potassium tert-butoxide. Studies indicate that the pathway involves (i) the formation of indole radical anions followed by fragmentation of the indole C2–N bond, and (ii) a ring-closing reaction that follows a potassium-ion dependent hydrogen atom transfer step. Unexpected behaviors of ‘radical-trap’ substrates prove very helpful in framing the proposed mechanism. N-Arylindoles are transformed into dihydroacridines in a new type of rearrangement, through heating with triethylsilane and potassium tert-butoxide.![]()
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Affiliation(s)
- Andrew J Smith
- Department of Pure and Applied Chemistry, University of Strathclyde 295 Cathedral Street Glasgow G1 1XL UK
| | - Daniela Dimitrova
- Department of Pure and Applied Chemistry, University of Strathclyde 295 Cathedral Street Glasgow G1 1XL UK
| | - Jude N Arokianathar
- Department of Pure and Applied Chemistry, University of Strathclyde 295 Cathedral Street Glasgow G1 1XL UK
| | - Krystian Kolodziejczak
- Department of Pure and Applied Chemistry, University of Strathclyde 295 Cathedral Street Glasgow G1 1XL UK
| | - Allan Young
- Department of Pure and Applied Chemistry, University of Strathclyde 295 Cathedral Street Glasgow G1 1XL UK
| | - Mark Allison
- Department of Pure and Applied Chemistry, University of Strathclyde 295 Cathedral Street Glasgow G1 1XL UK
| | - Darren L Poole
- GlaxoSmithKline Medicines Research Centre Gunnels Wood Road, Stevenage SG1 2NY UK
| | - Stuart G Leach
- GlaxoSmithKline Medicines Research Centre Gunnels Wood Road, Stevenage SG1 2NY UK
| | - John A Parkinson
- Department of Pure and Applied Chemistry, University of Strathclyde 295 Cathedral Street Glasgow G1 1XL UK
| | - Tell Tuttle
- Department of Pure and Applied Chemistry, University of Strathclyde 295 Cathedral Street Glasgow G1 1XL UK
| | - John A Murphy
- Department of Pure and Applied Chemistry, University of Strathclyde 295 Cathedral Street Glasgow G1 1XL UK
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9
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Alkayal A, Tabas V, Montanaro S, Wright IA, Malkov AV, Buckley BR. Harnessing Applied Potential: Selective β-Hydrocarboxylation of Substituted Olefins. J Am Chem Soc 2020; 142:1780-1785. [DOI: 10.1021/jacs.9b13305] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Anas Alkayal
- Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom
| | - Volodymyr Tabas
- Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom
| | - Stephanie Montanaro
- Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom
| | - Iain A. Wright
- Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom
| | - Andrei V. Malkov
- Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom
| | - Benjamin R. Buckley
- Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, United Kingdom
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10
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Laudenschlager JE, Combee LA, Hilinski MK. Intermolecular scandium triflate-promoted nitrene-transfer [5 + 1] cycloadditions of vinylcyclopropanes. Org Biomol Chem 2019; 17:9413-9417. [PMID: 31641723 DOI: 10.1039/c9ob01858a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sc(OTf)3-promoted [5 + 1] cycloaddition of vinylcyclopropanes with PhINTs is reported, enabling the regioselective preparation of a range of 1,2,3,6-tetrahydropyridine scaffolds under mild conditions. This represents the second example of a [5 + 1] nitrene-transfer cycloaddition and exhibits complementary substrate scope to the antecedent work, expanding the range of N-heterocycles accessible via this strategy.
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Affiliation(s)
- Julie E Laudenschlager
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, USA.
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11
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Xiao X, Woods BP, Xiu W, Hoye TR. Benzocyclobutadienes: An Unusual Mode of Access Reveals Unusual Modes of Reactivity. Angew Chem Int Ed Engl 2018; 57:9901-9905. [PMID: 29874408 PMCID: PMC6296485 DOI: 10.1002/anie.201803872] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 05/23/2018] [Indexed: 10/14/2022]
Abstract
The reaction of an aryne with an alkyne to generate a benzocyclobutadiene (BCB) intermediate is rare. We report here examples of this reaction, revealed by Diels-Alder trapping of the BCB by either pendant or external electron-deficient alkynes. Mechanistic delineation of the reaction course is supported by DFT calculations. A three-component process joining the benzyne first with an electron-rich and then with an electron-poor alkyne was uncovered. Reactions in which the BCB functions in a rarely observed role as a 4π diene component in Diels-Alder reactions are reported. The results also shed new light on aspects of the hexadehydro-Diels-Alder reaction used to generate the benzynes.
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Affiliation(s)
- Xiao Xiao
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota, 55455, USA
| | - Brian P Woods
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota, 55455, USA
| | - Wen Xiu
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota, 55455, USA
| | - Thomas R Hoye
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota, 55455, USA
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12
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Xiao X, Woods BP, Xiu W, Hoye TR. Benzocyclobutadienes: An Unusual Mode of Access Reveals Unusual Modes of Reactivity. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201803872] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Xiao Xiao
- Department of Chemistry University of Minnesota 207 Pleasant St. SE Minneapolis Minnesota 55455 USA
| | - Brian P. Woods
- Department of Chemistry University of Minnesota 207 Pleasant St. SE Minneapolis Minnesota 55455 USA
| | - Wen Xiu
- Department of Chemistry University of Minnesota 207 Pleasant St. SE Minneapolis Minnesota 55455 USA
| | - Thomas R. Hoye
- Department of Chemistry University of Minnesota 207 Pleasant St. SE Minneapolis Minnesota 55455 USA
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13
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Teng S, Tessensohn ME, Webster RD, Zhou JS. Palladium-Catalyzed Intermolecular Heck-Type Reaction of Epoxides. ACS Catal 2018. [DOI: 10.1021/acscatal.8b02029] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Shenghan Teng
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Malcolm E. Tessensohn
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Richard D. Webster
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Jianrong Steve Zhou
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
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14
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Phelan JP, Lang SB, Compton JS, Kelly CB, Dykstra R, Gutierrez O, Molander GA. Redox-Neutral Photocatalytic Cyclopropanation via Radical/Polar Crossover. J Am Chem Soc 2018; 140:8037-8047. [PMID: 29916711 DOI: 10.1021/jacs.8b05243] [Citation(s) in RCA: 136] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A benchtop stable, bifunctional reagent for the redox-neutral cyclopropanation of olefins has been developed. Triethylammonium bis(catecholato)iodomethylsilicate can be readily prepared on multigram scale. Using this reagent in combination with an organic photocatalyst and visible light, cyclopropanation of an array of olefins, including trifluoromethyl- and pinacolatoboryl-substituted alkenes, can be accomplished in a matter of hours. The reaction is highly tolerant of traditionally reactive functional groups (carboxylic acids, basic heterocycles, alkyl halides, etc.) and permits the chemoselective cyclopropanation of polyolefinated compounds. Mechanistic interrogation revealed that the reaction proceeds via a rapid anionic 3- exo- tet ring closure, a pathway consistent with experimental and computational data.
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Affiliation(s)
- James P Phelan
- Roy and Diana Vagelos Laboratories, Department of Chemistry , University of Pennsylvania , 231 South 34th Street , Philadelphia , Pennsylvania 19104-6323 , United States
| | - Simon B Lang
- Roy and Diana Vagelos Laboratories, Department of Chemistry , University of Pennsylvania , 231 South 34th Street , Philadelphia , Pennsylvania 19104-6323 , United States
| | - Jordan S Compton
- Roy and Diana Vagelos Laboratories, Department of Chemistry , University of Pennsylvania , 231 South 34th Street , Philadelphia , Pennsylvania 19104-6323 , United States
| | - Christopher B Kelly
- Roy and Diana Vagelos Laboratories, Department of Chemistry , University of Pennsylvania , 231 South 34th Street , Philadelphia , Pennsylvania 19104-6323 , United States
| | - Ryan Dykstra
- Department of Chemistry and Biochemistry , University of Maryland , College Park , Maryland 20742 , United States
| | - Osvaldo Gutierrez
- Department of Chemistry and Biochemistry , University of Maryland , College Park , Maryland 20742 , United States
| | - Gary A Molander
- Roy and Diana Vagelos Laboratories, Department of Chemistry , University of Pennsylvania , 231 South 34th Street , Philadelphia , Pennsylvania 19104-6323 , United States
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15
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Hosseini SN, Johnston JR, West FG. Evidence for heterolytic cleavage of a cyclic oxonium ylide: implications for the mechanism of the Stevens [1,2]-shift. Chem Commun (Camb) 2017; 53:12654-12656. [PMID: 29125612 DOI: 10.1039/c7cc07716e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Formation and rearrangement of several oxonium ylides containing cyclopropylcarbinyl migrating groups were studied. Efficient ring-contraction by [1,2]-shift to form cyclopropane-substituted cyclobutanones was observed, with no competing cyclopropane fragmentation. Substitution with the hypersensitive mechanistic probe (trans,trans-2-methoxy-3-phenylcyclopropyl)methyl led to cyclopropane fragmentation via an apparent heterolytic pathway, providing the first evidence for ion pair intermediates from ylide cleavage, and suggesting a possible alternative heterolytic mechanism for the Stevens [1,2]-shift.
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Affiliation(s)
- Seyedeh Nargess Hosseini
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, Alberta T6G 2G2, Canada.
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16
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Ayub R, Papadakis R, Jorner K, Zietz B, Ottosson H. Cyclopropyl Group: An Excited-State Aromaticity Indicator? Chemistry 2017; 23:13684-13695. [PMID: 28683165 DOI: 10.1002/chem.201701404] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Indexed: 01/11/2023]
Abstract
The cyclopropyl (cPr) group, which is a well-known probe for detecting radical character at atoms to which it is connected, is tested as an indicator for aromaticity in the first ππ* triplet and singlet excited states (T1 and S1 ). Baird's rule says that the π-electron counts for aromaticity and antiaromaticity in the T1 and S1 states are opposite to Hückel's rule in the ground state (S0 ). Our hypothesis is that the cPr group, as a result of Baird's rule, will remain closed when attached to an excited-state aromatic ring, enabling it to be used as an indicator to distinguish excited-state aromatic rings from excited-state antiaromatic and nonaromatic rings. Quantum chemical calculations and photoreactivity experiments support our hypothesis; calculated aromaticity indices reveal that openings of cPr substituents on [4n]annulenes ruin the excited-state aromaticity in energetically unfavorable processes. Yet, polycyclic compounds influenced by excited-state aromaticity (e.g., biphenylene), as well as 4nπ-electron heterocycles with two or more heteroatoms represent limitations.
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Affiliation(s)
- Rabia Ayub
- Department of Chemistry-BMC, Uppsala University, Box 576, 751 23, Uppsala, Sweden.,Department of Chemistry-Ångström Laboratory, Uppsala University, Box 523, 751 20, Uppsala, Sweden
| | - Raffaello Papadakis
- Department of Chemistry-BMC, Uppsala University, Box 576, 751 23, Uppsala, Sweden.,Department of Chemistry-Ångström Laboratory, Uppsala University, Box 523, 751 20, Uppsala, Sweden
| | - Kjell Jorner
- Department of Chemistry-BMC, Uppsala University, Box 576, 751 23, Uppsala, Sweden.,Department of Chemistry-Ångström Laboratory, Uppsala University, Box 523, 751 20, Uppsala, Sweden
| | - Burkhard Zietz
- Department of Chemistry-Ångström Laboratory, Uppsala University, Box 523, 751 20, Uppsala, Sweden
| | - Henrik Ottosson
- Department of Chemistry-BMC, Uppsala University, Box 576, 751 23, Uppsala, Sweden.,Department of Chemistry-Ångström Laboratory, Uppsala University, Box 523, 751 20, Uppsala, Sweden
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17
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Poremba KE, Kadunce NT, Suzuki N, Cherney AH, Reisman SE. Nickel-Catalyzed Asymmetric Reductive Cross-Coupling To Access 1,1-Diarylalkanes. J Am Chem Soc 2017; 139:5684-5687. [PMID: 28406620 PMCID: PMC5851002 DOI: 10.1021/jacs.7b01705] [Citation(s) in RCA: 196] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
An asymmetric Ni-catalyzed reductive cross-coupling of (hetero)aryl iodides and benzylic chlorides has been developed to prepare enantioenriched 1,1-diarylalkanes. As part of these studies, a new chiral bioxazoline ligand, 4-heptyl-BiOX (L1), was developed in order to obtain products in synthetically useful yield and enantioselectivity. The reaction tolerates a variety of heterocyclic coupling partners, including pyridines, pyrimidines, indoles, and piperidines.
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Affiliation(s)
- Kelsey E. Poremba
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, United States
| | - Nathaniel T. Kadunce
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, United States
| | - Naoyuki Suzuki
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, United States
| | - Alan H. Cherney
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, United States
| | - Sarah E. Reisman
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, United States
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18
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Suzuki N, Hofstra JL, Poremba KE, Reisman SE. Nickel-Catalyzed Enantioselective Cross-Coupling of N-Hydroxyphthalimide Esters with Vinyl Bromides. Org Lett 2017; 19:2150-2153. [PMID: 28375631 PMCID: PMC5868419 DOI: 10.1021/acs.orglett.7b00793] [Citation(s) in RCA: 135] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
An enantioselective Ni-catalyzed cross-coupling of N-hydroxyphthalimide esters with vinyl bromides is reported. The reaction proceeds under mild conditions and uses tetrakis(N,N-dimethylamino)ethylene as a terminal organic reductant. Good functional group tolerance is demonstrated, with over 20 examples of reactions that proceed with >90% ee.
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Affiliation(s)
| | | | - Kelsey E. Poremba
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Sarah E. Reisman
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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19
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Prina Cerai G, Morandi B. Atom-economical cobalt-catalysed regioselective coupling of epoxides and aziridines with alkenes. Chem Commun (Camb) 2016; 52:9769-72. [DOI: 10.1039/c6cc04410g] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
An atom-economical cobalt-catalysed regioselective coupling of epoxides and aziridines with alkenes is reported.
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Affiliation(s)
| | - Bill Morandi
- Max-Planck-Institut für Kohlenforschung
- Mülheim an der Ruhr
- Germany
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20
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Ingold KU, Bowry VW. Why Are Organotin Hydride Reductions of Organic Halides So Frequently Retarded? Kinetic Studies, Analyses, and a Few Remedies. J Org Chem 2015; 80:1321-31. [DOI: 10.1021/jo502710a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- K. U. Ingold
- National Research Council, Ottawa, Ontario K1A 0R6, Canada
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21
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Ranaweera RAAU, Weragoda GK, Bain J, Watanabe S, Abe M, Gudmundsdottir AD. Photolysis of acetophenone derivatives with α-cyclopropyl substituents. J PHYS ORG CHEM 2014. [DOI: 10.1002/poc.3389] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
| | | | - John Bain
- Department of Chemistry; University of Cincinnati; Cincinnati OH 45221-0172 USA
| | - Shinji Watanabe
- Department of Chemistry, Graduate School of Science; Hiroshima University; 1-3-1 Kagamiyama Higashi-Hiroshima Hiroshima 739 -8526 Japan
| | - Manabu Abe
- Department of Chemistry, Graduate School of Science; Hiroshima University; 1-3-1 Kagamiyama Higashi-Hiroshima Hiroshima 739 -8526 Japan
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22
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Han A, Spataru T, Hartung J, Li G, Norton JR. Effect of double-bond substituents on the rate of cyclization of α-carbomethoxyhex-5-enyl radicals. J Org Chem 2014; 79:1938-46. [PMID: 24502650 DOI: 10.1021/jo402499w] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rate constants have been calculated, and compared with experimental results, for the cyclizations of 1-carbomethoxy-1-methyl-5-hexenyl radicals (2) with various substituents on C6. The calculations have been done by DFT at the B3LYP/6-311++G** level of theory. They show considerable interaction between C5 and the radical centers even in the ground state of all of the radicals 2. Experimentally, the radicals have been generated by H(•) transfer to the corresponding acrylate esters 1 and the yields of cyclized products compared to the calculated rate constants. (The "cyclized products" include those from cyclohydrogenation, 4, and those from cycloisomerization, 9.) Two phenyl substituents on C6 (2i), or a phenyl and a methyl substituent (2g, 2h), increase the rate of cyclization, but a single phenyl substituent on C6 produces a greater increase. The calculations show that the two phenyl substituents are twisted in the transition state for cyclization, while a single phenyl substituent remains flat in that transition state. A methyl substituent on C6 along with a single phenyl causes the phenyl to twist in the transition state and decreases the rate constant for cyclization below that of the H/Ph-substituted 2e, 2f.
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Affiliation(s)
- Arthur Han
- Department of Chemistry, Columbia University , 3000 Broadway, New York, New York 10027, United States
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23
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Kontokosta D, Mueller DS, Wang HY, Anderson LL. Preparation of α-imino aldehydes by [1,3]-rearrangements of O-alkenyl oximes. Org Lett 2013; 15:4830-3. [PMID: 24004173 DOI: 10.1021/ol402237w] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The synthesis of α-imino aldehydes has been achieved through the thermal [1,3]-rearrangement of O-alkenyl benzophenone oximes. A copper-mediated C-O bond coupling between benzophenone oxime and alkenyl boronic acids provides facile access to the required O-alkenyl oximes and a Horner-Wadsworth-Emmons olefination can be applied to the α-imino aldehyde products to give γ-imino-α,β-unsaturated esters. The scope of the method is described and mechanistic experiments are discussed.
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Affiliation(s)
- Dimitra Kontokosta
- Department of Chemistry, University of Illinois at Chicago , 845 West Taylor Street, Chicago, Illinois 60607, United States
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24
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Wang Q, Sheng X, Horner JH, Newcomb M. Quantitative production of compound I from a cytochrome P450 enzyme at low temperatures. Kinetics, activation parameters, and kinetic isotope effects for oxidation of benzyl alcohol. J Am Chem Soc 2009; 131:10629-36. [PMID: 19572732 DOI: 10.1021/ja9031105] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cytochrome P450 enzymes are commonly thought to oxidize substrates via an iron(IV)-oxo porphyrin radical cation transient termed Compound I, but kinetic studies of P450 Compounds I are essentially nonexistent. We report production of Compound I from cytochrome P450 119 (CYP119) in high conversion from the corresponding Compound II species at low temperatures in buffer mixtures containing 50% glycerol by photolysis with 365 nm light from a pulsed lamp. Compound I was studied as a reagent in oxidations of benzyl alcohol and its benzylic mono- and dideuterio isotopomers. Pseudo-first-order rate constants obtained at -50 degrees C with concentrations of substrates between 1.0 and 6.0 mM displayed saturation kinetics that gave binding constants for the substrate in the Compound I species (K(bind)) and first-order rate constants for the oxidation reactions (k(ox)). Representative results are K(bind) = 214 M(-1) and k(ox) = 0.48 s(-1) for oxidation of benzyl alcohol. For the dideuterated substrate C(6)H(5)CD(2)OH, kinetics were studied between -50 and -25 degrees C, and a van't Hoff plot for complexation and an Arrhenius plot for the oxidation reaction were constructed. The H/D kinetic isotope effects (KIEs) at -50 degrees C were resolved into a large primary KIE (P = 11.9) and a small, inverse secondary KIE (S = 0.96). Comparison of values extrapolated to 22 degrees C of both the rate constant for oxidation of C(6)H(5)CD(2)OH and the KIE for the nondeuterated and dideuterated substrates to values obtained previously in laser flash photolysis experiments suggested that tunneling could be a significant component of the total rate constant at -50 degrees C.
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Affiliation(s)
- Qin Wang
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, USA
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25
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Hazimeh H, Mattalia JM, Marchi-Delapierre C, Kanoufi F, Combellas C, Chanon M. Structural Effects in Radical Clocks and Mechanisms of Grignard Reagent Formation: Special Effect of a Phenyl Substituent in a Radical Clock when the Crossroads of Selectivity is at a Metal/Solution Interface. European J Org Chem 2009. [DOI: 10.1002/ejoc.200900096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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26
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Salamone M, Bietti M, Calcagni A, Gente G. Phenyl Bridging in Ring-Substituted Cumyloxyl Radicals. A Product and Time-Resolved Kinetic Study. Org Lett 2009; 11:2453-6. [DOI: 10.1021/ol900635z] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Michela Salamone
- Dipartimento di Scienze e Tecnologie Chimiche, Università “Tor Vergata”, Via della Ricerca Scientifica, 1 I-00133 Rome, Italy
| | - Massimo Bietti
- Dipartimento di Scienze e Tecnologie Chimiche, Università “Tor Vergata”, Via della Ricerca Scientifica, 1 I-00133 Rome, Italy
| | - Alessandra Calcagni
- Dipartimento di Scienze e Tecnologie Chimiche, Università “Tor Vergata”, Via della Ricerca Scientifica, 1 I-00133 Rome, Italy
| | - Giacomo Gente
- Dipartimento di Scienze e Tecnologie Chimiche, Università “Tor Vergata”, Via della Ricerca Scientifica, 1 I-00133 Rome, Italy
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27
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Sheng X, Zhang H, Hollenberg PF, Newcomb M. Kinetic isotope effects in hydroxylation reactions effected by cytochrome P450 compounds I implicate multiple electrophilic oxidants for P450-catalyzed oxidations. Biochemistry 2009; 48:1620-7. [PMID: 19182902 DOI: 10.1021/bi802279d] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Kinetic isotope effects were measured for oxidations of (S,S)-2-(p-trifluoromethylphenyl)cyclopropylmethane containing zero, two, and three deuterium atoms on the methyl group by Compounds I from the cytochrome P450 enzymes CYP119 and CYP2B4 at 22 degrees C. The oxidations displayed saturation kinetics, which permitted solution of both binding constants (K(bind)) and first-order oxidation rate constants (k(ox)) for both enzymes with the three substrates. The binding constant for CYP2B4 Compound I was about 1 order of magnitude greater than that for CYP119 Compound I, but the oxidation rate constants were similar for the two. In oxidations of 1-d(0), k(ox) = 10.4 s(-1) for CYP119 Compound I, and k(ox) = 12.4 s(-1) for CYP2B4 Compound I. Primary kinetic isotope effects (P) and secondary kinetic isotope effects (S) were obtained from the results with the three isotopomers. The primary KIEs were large, P = 9.8 and P = 8.9 for CYP119 and CYP2B4 Compounds I, respectively, and the secondary KIEs were small and normal, S = 1.07 and S = 1.05, respectively. Large intermolecular KIEs for 1-d(0) and 1-d(3) of k(H)/k(D) = 11.2 and 9.8 found for the two Compounds I contrast with small intermolecular KIEs obtained previously for the same substrate in P450-catalyzed oxidations; these differences suggest that a second electrophilic oxidant, presumably iron-complexed hydrogen peroxide, is important in cytochrome P450 oxidations under turnover conditions.
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Affiliation(s)
- Xin Sheng
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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28
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Dohi T, Takenaga N, Goto A, Fujioka H, Kita Y. Clean and Efficient Benzylic C−H Oxidation in Water Using a Hypervalent Iodine Reagent: Activation of Polymeric Iodosobenzene with KBr in the Presence of Montmorillonite-K10. J Org Chem 2008; 73:7365-8. [DOI: 10.1021/jo8012435] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Toshifumi Dohi
- Graduate School of Pharmaceutical Sciences, Osaka University,1-6 Yamada-oka, Suita, Osaka, 565-0871 Japan
| | - Naoko Takenaga
- Graduate School of Pharmaceutical Sciences, Osaka University,1-6 Yamada-oka, Suita, Osaka, 565-0871 Japan
| | - Akihiro Goto
- Graduate School of Pharmaceutical Sciences, Osaka University,1-6 Yamada-oka, Suita, Osaka, 565-0871 Japan
| | - Hiromichi Fujioka
- Graduate School of Pharmaceutical Sciences, Osaka University,1-6 Yamada-oka, Suita, Osaka, 565-0871 Japan
| | - Yasuyuki Kita
- Graduate School of Pharmaceutical Sciences, Osaka University,1-6 Yamada-oka, Suita, Osaka, 565-0871 Japan
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29
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Lee JM, Park EJ, Cho SH, Chang S. Cu-Facilitated C−O Bond Formation Using N-Hydroxyphthalimide: Efficient and Selective Functionalization of Benzyl and Allylic C−H Bonds. J Am Chem Soc 2008; 130:7824-5. [DOI: 10.1021/ja8031218] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ji Min Lee
- Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Eun Ju Park
- Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Seung Hwan Cho
- Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
| | - Sukbok Chang
- Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea
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30
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DeZutter CB, Horner JH, Newcomb M. Rate Constants for 1,5- and 1,6-Hydrogen Atom Transfer Reactions of Mono-, Di-, and Tri-aryl-substituted Donors, Models for Hydrogen Atom Transfers in Polyunsaturated Fatty Acid Radicals. J Phys Chem A 2008; 112:1891-6. [PMID: 18269270 DOI: 10.1021/jp710750f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Christopher B. DeZutter
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607
| | - John H. Horner
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607
| | - Martin Newcomb
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607
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31
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Hirsekorn KF, Hulley EB, Wolczanski PT, Cundari TR. Olefin Substitution in (silox)3M(olefin) (silox = tBu3SiO; M = Nb, Ta): The Role of Density of States in Second vs Third Row Transition Metal Reactivity. J Am Chem Soc 2008; 130:1183-96. [DOI: 10.1021/ja074972j] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kurt F. Hirsekorn
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, and Department of Chemistry, University of North Texas, Box 305070, Denton, Texas 76203-5070
| | - Elliott B. Hulley
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, and Department of Chemistry, University of North Texas, Box 305070, Denton, Texas 76203-5070
| | - Peter T. Wolczanski
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, and Department of Chemistry, University of North Texas, Box 305070, Denton, Texas 76203-5070
| | - Thomas R. Cundari
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, and Department of Chemistry, University of North Texas, Box 305070, Denton, Texas 76203-5070
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32
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Newcomb M, Chandrasena REP, Lansakara-P DSP, Kim HY, Lippard SJ, Beauvais LG, Murray LJ, Izzo V, Hollenberg PF, Coon MJ. Desaturase reactions complicate the use of norcarane as a mechanistic probe. Unraveling the mixture of twenty-plus products formed in enzyme-catalyzed oxidations of norcarane. J Org Chem 2007; 72:1121-7. [PMID: 17288366 PMCID: PMC2495027 DOI: 10.1021/jo061864r] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Norcarane, bicyclo[4.1.0]heptane, has been widely used as a mechanistic probe in studies of oxidations catalyzed by several iron-containing enzymes. We report here that, in addition to oxygenated products, norcarane is also oxidized by iron-containing enzymes in desaturase reactions that give 2-norcarene and 3-norcarene. Furthermore, secondary products from further oxidation reactions of the norcarenes are produced in yields that are comparable to those of the minor products from oxidation of the norcarane. We studied oxidations catalyzed by a representative spectrum of iron-containing enzymes including four cytochrome P450 enzymes, CYP2B1, CYPDelta2B4, CYPDelta2E1, and CYPDelta2E1 T303A, and three diiron enzymes, soluble methane monooxygenase (sMMO) from Methylococcus capsulatus (Bath), toluene monooxygenase (ToMO) from Pseudomonas stutzeri OX1, and phenol hydroxylase (PH) from Pseudomonas stutzeri OX1. 2-Norcarene and 3-norcarene and their oxidation products were found in all reaction mixtures, accounting for up to half of the oxidation products in some cases. In total, more than 20 oxidation products were identified from the enzyme-catalyzed reactions of norcarane. The putative radical-derived product from the oxidation of norcarane, 3-hydroxymethylcyclohexene (21), and the putative cation-derived product from the oxidation of norcarane, cyclohept-3-enol (22), coelute with other oxidation products on low-polarity GC columns. The yields of product 21 found in this study are smaller than those previously reported for the same or similar enzymes in studies where the products from norcarene oxidations were ignored, and therefore, the limiting values for lifetimes of radical intermediates produced in the enzyme-catalyzed oxidation reactions are shorter than those previously reported.
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Affiliation(s)
- Martin Newcomb
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607, USA.
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33
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Horner JH, Newcomb M. Kinetic studies of a fast, reversible alkene radical cation cyclization reaction. J Org Chem 2007; 72:1609-16. [PMID: 17256989 DOI: 10.1021/jo061868w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The radical cation formed by mesylate heterolysis from the 1,1-dimethyl-7,7-diphenyl-2-mesyloxy-6-heptenyl radical was studied in several solvents. Computational results suggest that the initially formed acyclic radical cation is a resonance hybrid with partial positive charge in both double bonds of 1,1-diphenyl-7-methyl-1,6-octadiene (10). Thiophenol trapping was used as the competing reaction for kinetic determinations. The acyclic radical cation rapidly equilibrates with a cyclic distonic radical cation, and thiophenol trapping gives acyclic product 10 and cyclic products, mainly trans-1-(diphenylmethyl)-2-(1-methylethenyl)cyclopentane (11). The rate constants for cyclization at ambient temperature were k = (0.5-2) x 10(10)(s-1), and those for ring opening were k = (1.5-9) x 10(10)(s-1). Laser flash photolysis studies in several solvents show relatively slow processes (k = (2.5-260) x 10(5)(s-1) that involve rate-limiting trapping reactions for the equilibrating radical cations. In mixtures of fluoroalcohols RfCH2OH in trifluoromethylbenzene, variable-temperature studies display small, and in one case a negative, activation energies, requiring equilibration reactions prior to the rate-limiting processes. Fast equilibration of acyclic and cyclic radical cations implies that product ratios can be controlled by the populations of the acyclic and cyclic species and relative rate constants for trapping each.
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Affiliation(s)
- John H Horner
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607, USA
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34
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Newcomb M, Lansakara-P DSP, Kim HY, Chandrasena REP, Lippard SJ, Beauvais LG, Murray LJ, Izzo V, Hollenberg PF, Coon MJ. Products from enzyme-catalyzed oxidations of norcarenes. J Org Chem 2007; 72:1128-33. [PMID: 17288367 PMCID: PMC2497458 DOI: 10.1021/jo061865j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent studies revealed that norcarane (bicyclo[4.1.0]heptane) is oxidized to 2-norcarene (bicyclo[4.1.0]-hept-2-ene) and 3-norcarene (bicyclo[4.1.0]hept-3-ene) by iron-containing enzymes and that secondary oxidation products from the norcarenes complicate mechanistic probe studies employing norcarane as the substrate (Newcomb, M.; Chandrasena, R. E. P.; Lansakara-P., D. S. P.; Kim, H.-Y.; Lippard, S. J.; Beauvais, L. G.; Murray, L. J.; Izzo, V.; Hollenberg, P. F.; Coon, M. J. J. Org. Chem. 2007, 72, 1121-1127). In the present work, the product profiles from the oxidations of 2-norcarene and 3-norcarene by several enzymes were determined. Most of the products were identified by GC and GC-mass spectral comparison to authentic samples produced independently; in some cases, stereochemical assignments were made or confirmed by 2D NMR analysis of the products. The enzymes studied in this work were four cytochrome P450 enzymes, CYP2B1, CYPDelta2E1, CYPDelta2E1 T303A, and CYPDelta2B4, and three diiron-containing enzymes, soluble methane monooxygenase (sMMO) from Methylococcus capsulatus (Bath), toluene monooxygenase (ToMO) from Pseudomonas stutzeri OX1, and phenol hydroxylase (PH) from Pseudomonas stutzeri OX1. The oxidation products from the norcarenes identified in this work are 2-norcaranone, 3-norcaranone, syn- and anti-2-norcarene oxide, syn- and anti-3-norcarene oxide, syn- and anti-4-hydroxy-2-norcarene, syn- and anti-2-hydroxy-3-norcarene, 2-oxo-3-norcarene, 4-oxo-2-norcarene, and cyclohepta-3,5-dienol. Two additional, unidentified oxidation products were observed in low yields in the oxidations. In matched oxidations, 3-norcarene was a better substrate than 2-norcarene in terms of turnover by factors of 1.5-15 for the enzymes studied here. The oxidation products found in enzyme-catalyzed oxidations of the norcarenes are useful for understanding the complex product mixtures obtained in norcarane oxidations.
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Affiliation(s)
- Martin Newcomb
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607, USA.
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35
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Maddess ML, Mainetti E, Harrak Y, Brancour C, Devin P, Dhimane AL, Fensterbank L, Malacria M. Preparation of fused polycyclic vinylcyclopropanes via radical cascade reactions. Chem Commun (Camb) 2007:936-8. [PMID: 17311126 DOI: 10.1039/b618156b] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Radical cascades employing (dichloromethyl)dimethylsilyl ethers as both a point of radical initiation and termination, allow efficient entry to fused polycyclic cyclopropanes, and are also suitable for the design of other radical processes terminated by beta-elimination of chloride.
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Affiliation(s)
- Matthew L Maddess
- Laboratorie de Chimie Organique, UMR CNRS 7611, Institut de Chimie Moléculaire FR 2769, Université Pierre et Marie Curie - Paris 6, Case 229, 4 Place Jussieu, 75005, Paris, France
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36
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Goddard JP, Gomez C, Brebion F, Beauvière S, Fensterbank L, Malacria M. Highly diastereoselective ionic/radical domino reactions: single electron transfer induced cyclization of bis-sulfoxides. Chem Commun (Camb) 2007:2929-31. [PMID: 17622434 DOI: 10.1039/b705284g] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
SET oxidation of bis-sulfinyl anions has enabled the uses of bis-sulfinyl radical as a synthetic equivalent of chiral acyl and methylene radicals involved in tandem reactions leading to the enantioselective construction of various carbo- and heterocyclic derivatives.
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Affiliation(s)
- Jean-Philippe Goddard
- Laboratoire de Chimie Organique (UMR CNRS 7611), Institut de chimie moléculaire FR 2769, Université Pierre et Marie Curie-Paris 6, case 229, 4 place Jussieu, 75252 Paris cedex 05, France
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37
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Ajjou AN, Riahi A, Chatterjee D, Muzart J. Chromium-catalyzed oxidation of benzylcyclopropane with tert-butyl hydroperoxide. CATAL COMMUN 2006. [DOI: 10.1016/j.catcom.2006.01.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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38
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Bietti M, Fiorentini S, Pato IP, Salamone M. Oxygen Acidity of Ring Methoxylated 1,1-Diarylalkanol Radical Cations Bearing α-Cyclopropyl Groups. The Competition between O-Neophyl Shift and C−Cyclopropyl β-Scission in the Intermediate 1,1-Diarylalkoxyl Radicals. J Org Chem 2006; 71:3167-75. [PMID: 16599615 DOI: 10.1021/jo0600860] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A product and time-resolved kinetic study on the reactivity of the radical cations generated from cyclopropyl(4-methoxyphenyl)phenylmethanol (1) and cyclopropyl[bis(4-methoxyphenyl)]methanol (2) has been carried out in aqueous solution. In acidic solution, 1*+ and 2*+ display very low reactivities toward fragmentation, consistent with the presence of groups at Calpha (aryl and cyclopropyl) that after Calpha-Cbeta bond cleavage would produce relatively unstable carbon-centered radicals. In basic solution, 1*+ and 2*+ display oxygen acidity, undergoing -OH-induced deprotonation from the alpha-OH group, leading to the corresponding 1,1-diarylalkoxyl radicals 1r* and 2r*, respectively, as directly observed by time-resolved spectroscopy. The product distributions observed in the reactions of 1*+ and 2*+ under these conditions (cyclopropyl phenyl ketone, cyclopropyl(4-methoxyphenyl) ketone, and 4-methoxybenzophenone from 1*+; cyclopropyl(4-methoxyphenyl) ketone and 4,4'-dimethoxybenzophenone from 2*+) have been rationalized in terms of a water-induced competition between O-neophyl shift and C-cyclopropyl beta-scission in the intermediate 1,1-diarylalkoxyl radicals 1r* and 2r*.
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Affiliation(s)
- Massimo Bietti
- Dipartimento di Scienze e Tecnologie Chimiche, Università Tor Vergata, Via della Ricerca Scientifica, I-00133 Rome, Italy.
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Tzvetkov NT, Neumann B, Stammler HG, Mattay J. Photoreactions of Tricyclic α-Cyclopropyl Ketones and Unsaturated Enones – Synthesis of Polyquinanes and Analogous Ring Systems. European J Org Chem 2006. [DOI: 10.1002/ejoc.200500546] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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40
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Newcomb M, Chandrasena REP. Highly reactive electrophilic oxidants in cytochrome P450 catalysis. Biochem Biophys Res Commun 2005; 338:394-403. [PMID: 16168951 DOI: 10.1016/j.bbrc.2005.08.208] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2005] [Accepted: 08/24/2005] [Indexed: 11/28/2022]
Abstract
The cytochrome P450 enzymes effect a wide range of oxidations in nature including difficult hydroxylation reactions of unactivated C-H. Most of the high energy reactions of these catalysts appear to involve highly electrophilic active species. Attempts to detect the reactive transients in the enzymes have met with limited success, but evidence has accumulated that two distinct electrophilic oxidants are produced in the P450 enzymes. The consensus electrophilic oxidant termed "iron-oxo" is usually thought to be an analogue of Compound I, an iron(IV)-oxo porphyrin radical cation species, but it is possible that a higher energy electronic isomer of Compound I is required to account for the facility of the C-H oxidation reactions. The second electrophilic oxidant of P450 is speculative; circumstantial evidence suggests that this species is iron-complexed hydrogen peroxide, but this oxidant might be a second spin state of iron-oxo. This overview discusses recent studies directed at detection of the electrophilic oxidants in P450 enzymes and the accumulated evidence for two distinct species.
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Affiliation(s)
- Martin Newcomb
- Department of Chemistry, University of Illinois at Chicago, 845 W. Taylor St., Chicago, IL 60607, USA.
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41
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Aureliano Antunes CS, Bietti M, Ercolani G, Lanzalunga O, Salamone M. The Effect of Ring Substitution on the O-Neophyl Rearrangement of 1,1-Diarylalkoxyl Radicals. A Product and Time-Resolved Kinetic Study. J Org Chem 2005; 70:3884-91. [PMID: 15876075 DOI: 10.1021/jo0502448] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] A product and time-resolved kinetic study of the effect of ring substitution on the reactivity of 1,1-diarylalkoxyl radicals has been carried out. The radicals undergo an O-neophyl shift to give the isomeric 1-aryl-1-aryloxyalkyl radicals from which the corresponding aromatic ketones are formed. The rearrangement rate constants are influenced by ring substitution, increasing in the presence of electron-withdrawing substituents and decreasing in the presence of electron-donating ones. From the results of product and kinetic studies, the following migratory aptitudes have been obtained: 4-trifluoromethylphenyl > phenyl approximately = 4-methylphenyl > 4-methoxyphenyl. Excellent Hammett-type correlations between the sigma+ substituent constants and both the visible absorption band maxima and the rearrangement rate constants have been obtained. The experimental results indicate that the rearrangement is governed by electronic effects in the starting 1,1-diarylalkoxyl radicals, whereas the stability of the rearranged carbon-centered radical plays a minor role, in line with a reactant-like transition state, strongly supporting the hypothesis that the O-neophyl rearrangement of 1,1-diarylalkoxyl radicals proceeds through a concerted mechanism.
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Affiliation(s)
- Carla S Aureliano Antunes
- Dipartimento di Scienze e Tecnologie Chimiche, Università Tor Vergata, Via della Ricerca Scientifica, 1 I-00133 Rome, Italy
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42
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Tanko JM, Gillmore JG, Friedline R, Chahma M. Cyclopropylcarbinyl → Homoallyl-Type Ring Opening of Ketyl Radical Anions. Structure/Reactivity Relationships and the Contribution of Solvent/Counterion Reorganization to the Intrinsic Barrier. J Org Chem 2005; 70:4170-3. [PMID: 15876112 DOI: 10.1021/jo047917r] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] Following a protocol developed by Mathivanan, Johnston, and Wayner (J. Phys. Chem. 1995, 99, 8190-8195), the radical anions of several cyclopropyl- and oxiranyl-containing carbonyl compounds were generated in an effort to measure the rate constants for their ring opening (k(o)) by laser flash photolysis. The results of these experiments are compared to those obtained from earlier electrochemical studies, and the combined data set is used to rationalize the kinetics of radical anion ring opening in a general context by using Saveant's theory pertaining to stepwise dissociative electron transfer (Acc. Chem. Res. 1993, 26, 455-461). Compared to cyclopropylcarbinyl --> homoallyl rearrangements of neutral free radicals, at comparable driving force, the radical anion ring openings are slightly slower. The small difference in rate is attributed to the contribution of an additional, approximately 2 kcal/mol, solvent reorganization component for the radical anion rearrangements. The solvent reorganization energy for ring opening of these radical anions is believed to be small because the negative charge does not move appreciably in the progression reactant --> transition state --> product.
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Affiliation(s)
- J M Tanko
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
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43
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Chahma M, Li X, Phillips JP, Schwartz P, Brammer LE, Wang Y, Tanko JM. Activation/Driving Force Relationships for Cyclopropylcarbinyl → Homoallyl-Type Rearrangements of Radical Anions. J Phys Chem A 2005; 109:3372-82. [PMID: 16833672 DOI: 10.1021/jp050193i] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
By using direct and indirect electrochemical methods, rate constants (ko) for cyclopropane ring opening of radical anions derived from the one-electron reduction of trans-1-benzoyl-2-phenylcyclopropane, trans-1-benzoyl-2-vinylcyclopropane, 2-methylenecyclopropyl phenyl ketone, spiro[anthracene-9,1'-cyclopropan-10-one], 3-cyclopropylcyclohex-2-en-1-one, and 3-(1-methylcyclopropyl)cyclohex-2-en-1-one were determined. Qualitatively, rate constants for ring opening of these (and other cyclopropyl- and cyclobutyl-containing radical anions) can be rationalized on the basis of the thermodynamic stability of the radical anion, the ability of substituents on the cyclopropyl group to stabilize the radical portion of the distonic radical anion, and the stability of the enolate portion of the distonic radical anion. On the basis of this notion, a thermochemical cycle for estimating deltaG(o) for ring opening was presented. For simple cyclopropyl-containing ketyl anions, a reasonable correlation between log(ko) and deltaG(o) was found, and stepwise dissociative electron transfer theory was applied to rationalize the results. Activation energies calculated with density functional theory (UB3LYP/6-31+G*) correlate reasonably well with measured log(ko). The derived log(ko) and deltaG(o) and log(ko) vs E(a) plots provide the basis for a "calibration curve" to predict rate constants for ring opening of radical anions derived from carbonyl compounds, in general.
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Affiliation(s)
- M'hamed Chahma
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
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44
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Daublain P, Horner JH, Kuznetsov A, Newcomb M. Solvent polarity effects and limited acid catalysis in rearrangements of model radicals for the methylmalonyl-CoA mutase- and isobutyryl-CoA mutase-catalyzed isomerization reactions. J Am Chem Soc 2004; 126:5368-9. [PMID: 15113202 DOI: 10.1021/ja049913+] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The kinetics of reactions of models for the intermediate radicals formed in the methylmalonyl-CoA mutase- and isobutyryl-CoA mutase-catalyzed rearrangements were studied by laser flash photolysis methods. The aldehyde-containing model analogous to the propanal-3-yl radical reacted via 3-exo cyclization with rate constants that varied with solvent polarity (k in the range 2 x 105 to 1 x 107 s-1). The analogous methyl ketone-containing radical reacted 2 orders of magnitude less rapidly, and the ethylthiocarbonyl-containing radical analogue reacted too slowly for kinetic measurements. No acid catalysis was observed in acetic acid, but the CF3CO2H-complexed radicals reacted 1 order of magnitude faster than the uncomplexed radicals. The results indicate that catalysis of the 3-exo radical cyclizations of the radicals formed in the enzymes by hydrogen bonding to an acid, so-called "partial protonation", is not adequate for acceleration of the reactions to the point of kinetic competence. A dissociative mechanism for the radical rearrangements in nature is considered as an alternative.
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Affiliation(s)
- Pierre Daublain
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, USA
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45
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Jin S, Bryson TA, Dawson JH. Hydroperoxoferric heme intermediate as a second electrophilic oxidant in cytochrome P450-catalyzed reactions. J Biol Inorg Chem 2004; 9:644-53. [PMID: 15365901 DOI: 10.1007/s00775-004-0575-7] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2004] [Accepted: 06/24/2004] [Indexed: 10/26/2022]
Abstract
Experimental evidence supporting the catalytic activity of the peroxoferric and hydroperoxoferric cytochrome P450 intermediates as alternative oxidants to the compound I (ferryl) state in the oxygenation of organic substrates is reviewed. The peroxoferric P450 state is proposed to function as a nucleophile in the lyase step of the P450-aromatase reaction. Several systems are reviewed in which the hydroperoxoferric P450 intermediate likely functions as a second electrophilic oxidant, the "two-oxidants" model. These include alkene epoxidation, sulfoxidation, and hydroxylation of methyl groups on cyclopropane rings. The key use of the P450 mutants from different sources in which the conserved threonine in the distal substrate binding pocket is replaced with alanine, in order to minimize the formation of the compound I intermediate and unmask the reactivity of the hydroperoxoferric state, is emphasized. These data are discussed in the context of the "two-states" model, which proposes that the compound I P450 intermediate has both high- and low-spin states with different reactivities. A complicated reaction profile emerges for the wide range of P450 reactions involving up to three reactive intermediates, of which the most reactive, the compound I P450 state, has two spin states with different reactivities.
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Affiliation(s)
- Shengxi Jin
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA
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46
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Rüedi G, Nagel M, Hansen HJ. Three-Carbon Ring Expansion by Cyclopropane Insertion: Macrocyclic Musks from Readily Available C-12 Starting Materials. Org Lett 2004; 6:2989-91. [PMID: 15330665 DOI: 10.1021/ol0487027] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A thermal three-carbon ring expansion based on side chain ring insertion of a cyclopropane moiety is described. Flash vacuum pyrolysis (FVP) of 1-cyclopropyl-cycloalk-3-enol derivatives leads to the three-carbon ring expanded enones with clean retention of double bond geometry. Substrates bearing methyl groups on the cyclopropane ring undergo regioselective bond cleavage, allowing for the systematic preparation of selectively substituted macrocyclic musks from low-priced C-12 starting compounds.
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Affiliation(s)
- Georg Rüedi
- Organisch-chemisches Institut der Universität, 8057 Zürich, Switzerland.
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47
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Rüedi G, Hansen HJ. Cyclopropylcarbinyl radicals as three-carbon insertion units: easy synthesis of C-15 macrocyclic ketones by three-carbon ring expansion. Tetrahedron Lett 2004. [DOI: 10.1016/j.tetlet.2004.04.148] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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48
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Chandrasena REP, Vatsis KP, Coon MJ, Hollenberg PF, Newcomb M. Hydroxylation by the hydroperoxy-iron species in cytochrome P450 enzymes. J Am Chem Soc 2004; 126:115-26. [PMID: 14709076 DOI: 10.1021/ja038237t] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Intramolecular and intermolecular kinetic isotope effects (KIEs) were determined for hydroxylation of the enantiomers of trans-2-(p-trifluoromethylphenyl)cyclopropylmethane (1) by hepatic cytochrome P450 enzymes, P450s 2B1, Delta2B4, Delta2B4 T302A, Delta2E1, and Delta2E1 T303A. Two products from oxidation of the methyl group were obtained, unrearranged trans-2-(p-trifluoromethylphenyl)cyclopropylmethanol (2) and rearranged 1-(p-trifluoromethylphenyl)but-3-en-1-ol (3). In intramolecular KIE studies with dideuteriomethyl substrates (1-d(2)) and in intermolecular KIE studies with mixtures of undeuterated (1-d(0)) and trideuteriomethyl (1-d(3)) substrates, the apparent KIE for product 2 was consistently larger than the apparent KIE for product 3 by a factor of ca. 1.2. Large intramolecular KIEs found with 1-d(2) (k(H)/k(D) = 9-11 at 10 degrees C) were shown not to be complicated by tunneling effects by variable temperature studies with two P450 enzymes. The results require two independent isotope-sensitive processes in the overall hydroxylation reactions that are either competitive or sequential. Intermolecular KIEs were partially masked in all cases and largely masked for some P450s. The intra- and intermolecular KIE results were combined to determine the relative rate constants for the unmasking and hydroxylation reactions, and a qualitative correlation was found for the unmasking reaction and release of hydrogen peroxide from four of the P450 enzymes in the absence of substrate. The results are consistent with the two-oxidants model for P450 (Vaz, A. D. N.; McGinnity, D. F.; Coon, M. J. Proc. Natl. Acad. Sci. U.S.A. 1998, 95, 3555), which postulates that a hydroperoxy-iron species (or a protonated analogue of this species) is a viable electrophilic oxidant in addition to the consensus oxidant, iron-oxo.
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Affiliation(s)
- R Esala P Chandrasena
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, USA
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Newcomb M, Miranda N. An Accelerating−Reporting Group for Studies of Radical Heterolysis Reactions and Its Application in an Acid-Catalyzed Fragmentation Reaction of an α,β-Dimethoxy Radical. J Org Chem 2004; 69:6515-20. [PMID: 15387572 DOI: 10.1021/jo0357972] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The 2,2-diphenylcyclopropyl group was employed to accelerate reactions of alpha-methoxy radicals containing beta-leaving groups, to trap the products of either migration or heterolysis of the leaving group, and to provide a useful chromophore for laser flash photolysis kinetic studies. The reporting group biases reactions in favor of heterolytic fragmentation and most likely intercepts radical cations in ion pairs. The 1-methoxy-1-methyl-2-(diethylphosphatoxy)-2-(2,2-diphenylcyclopropyl)ethyl radical (3a) reacted faster than the kinetic resolution of the instrument (k > 2 x 10(8) s(-1)) in all solvents studied, and the 2-acetoxy analogue (3b) reacted much faster than related radicals that do not contain the cyclopropyl group (e.g., k = 1.1 x 10(6) s(-1) in CH3CN at ambient temperature). The rate constants and Arrhenius parameters for reactions of 3b indicated that the rate-limiting step in the reaction was heterolytic cleavage. The 1,2-dimethoxy-1-methyl-2-(2,2-diphenylcyclopropyl)ethyl radical (26) reacted in a general acid-catalyzed heterolysis reaction, and rate constants for protonation of the beta-methoxy group by a series of carboxylic acids were determined. The results suggest that acid-catalyzed reactions of beta-alkoxy radicals might be employed in synthetic conversions.
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Affiliation(s)
- Martin Newcomb
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607, USA.
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50
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Baik MH, Newcomb M, Friesner RA, Lippard SJ. Mechanistic studies on the hydroxylation of methane by methane monooxygenase. Chem Rev 2003; 103:2385-419. [PMID: 12797835 DOI: 10.1021/cr950244f] [Citation(s) in RCA: 355] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Mu-Hyun Baik
- Department of Chemistry, Columbia University, New York, New York 10027, USA
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